Synchronous communication system



- July 28, v R,F KD|RKES SYNCHRONOUS COMMUNICATION SYSTEM Filed Jan. 50. 1929 2 Sheets-Sheet. l

Sllventor Gtorneg July 28, 1931.

R. F. DIRKES SYNCHRONOUS COMMUNICATION SYSTEM Gttorneg A"liatentecl July k1931 smrceoneee commettent@ eieren l i `Appueen@ inea January '30, ieee'. senai n10. esente.

,i .This invention relates to a system Iof ysjvnohronizing =a plurality 'of vunits loca-ted at 'disftwbli's ed for communication.

An 'object 1olthis invention is :to devise la tantjloints from eeeh tot-heron a rcircuit esf .k-system whereby power station net-works or other-regular outside sources of uniform fre*- fqrt'enoy may be usejd forr 'synchronizing the elements in vl".syntehron'cms communiction 'syjsternA f This invention kwill `be kexplained as aplplied 'to 1(1)-21 'start-stop telegraph system, fand (2) `e multiplei'telegralph system. It is obvious, however, f its (rpplioatifon coi'ild be made 'to any communioition system 1n which it isneeessary to tween the sender an'd'reoeiveri e y y As is known tot-hose versed in the art', ,all start-stop printing mechanisms operated today rdrive their signalreceiving shft 'by 'a 'onpling arrangenient attached` to the rn'ain klr'ving unit. It sjls'oknown 'that et, different parts ofvtheirevolution of the main rdrl'vingmotor, there is nfspeed 'changerdue to: (a.)I diliaerenoes in 'load application `at* the 'different partsofvthe cycle, (b) differences speedV variation oi the motor due to flnctulations 'of voltage, endl 'dilfereirces'inl speed variation of 'the motor due tosur-,gin'g yof the governor, when a governor is used.

1t is necessary, therefore, fon the `phasing o 'sefehial lrnaehine to 'compensate i501" thesefdifferences 'as ferais possible. VThis is most generf-ally' ecompiished bythe insertion of a so-y -e'rlled rest pulse lin the ARoding, to allow the meehanisin to actually 'corne-t0 rest fora very shortfperiodl` and et the' same time to run the receiving motora't fws1igl`1tlv teisterfspeed that of tranemission'.flk This,` ofeonrs'e,

L ,speed VJfor the receivignnitfshaft. f,

is notlll that is tbbe desired, sin'ee with @neng-es of load, voltage, eto.,'on1yfanwfap vpranimation l`een be mede "asf't'o kthe proper 'gemme v,1eagire retener, tiene) "JAMAICA, New Yoeri, Atemnot-e Wieren 'einen meenemen rentner, or roer, @genereren or vom provide synchronism ber 'ermee f `lrnownto those' versed in the 'ar-t, t-ll-so-da'l'led etart=sftop receivinwgprintingnnits employ fa, light receiving shaft which -is kept in slyrrL chronismand phase with the sign-Tais trarre -"employs this saine 'shaft but diiers 'fromv the 'standard practie, in that l do' not 'drive 'the receiving shaft from the szvn'e source of pow'- 'er for all the heavier mechanism in the print; er, lont rather insert a new source of 'driving power-asexplained below.' Y 5 n in the following 'description 1 shxll refer f to the frccornp anying Vdrawings in which i: i

plied 'to a-start-etop system; f 'f f Figuresff zurdfS are diegrms serving to fi'llnstrate the proper operation 'fliny inventi'o'nyar'rd-f" f Figure@ illnstrzttesmy invention es ,mppled to a repeater station in 'e multiplex sys Referring to Figure "l, fa, pin .barrel 1 may represent there'cevin'g unit which is tilie'd 'in moet orrnsbf startLstop receiving nitrite. This pin ba'rrelmay eotiratedin any xone "I6 v'oit severaifdierent ways to designate between -a marking fs-ivgnal and "ausptr'cfing signal to be imparted to the. printing Gilly one zrne'thod is illustrated in the drawings in which, 2 Ais e permanent ereignet provided 'to witlir e ivoted forked 'armature @,worin" en a' 4coller 4- *of pin barrel l, said being slid-'ably "Connecte'dto fsheft 5. "Imis, upon lf'zuetu-eti'on of magnet 2,1pinJ-b'r'el i1 ifs enden the 'right or reffe 'filon-g :shaft epen- $5 .ing upon the polarity er 'the received-eigen. For purposes of explanation t time, '-l't @us disregard planetary 'gear unito on; Y5 @ne considerL shaft 5 mi more? shaft 'me y loney revolving unit. Shiny be" 'fgll lok synchronons motor, snleh is' 'sedffithe' present day clock systeilisr Itf`ffis,-vo"eo",7 understood k'that underkthe proper" 'bwer inf Huenee, 'that is, alternating eurren 'from *all number ofy vtheselino'toe 'can be kept in syn,- r-ehronisin and phase for extensive periods foi time. f' l v ,A tis obvior'is,thereforer thtsu'ch nfsnall sleek motoreold be Rept ineynehrbn'snend 14 phase either by attachment to a chain power service or by actuation from a separate power line fed from a central source. It is, of course, obvious that the better'and more4 eco- 5 nomical method of so phasing and synchronizing these motors would be from a chainconnected power system. Let us suppose, that motor 9 is connected to a source of alternating current power ofthe same frequency as motor 8, Vand that motor 9 is the driving v`source for a light transmitter brush 10Ywhich travels over asegmented face plate 11 from which the intelligence signals for the printing elementare sent. G1 and G2. represent alternating current power generators located at distant points (for example in different cities) and connected together by a distribution net-work represented by conductors NW. f r Inasmuch as motors 8 and 9 are being driven from the same or similar source of power of the'same frequency, they will keep in exact jphase relation with each other, and the signals sent over line 12, actuating line magnet 2, can be made, through pins 13, to actuate mechanisms commonly used in startstop printing systems, which in turn govern the actuation of the printers. Thus, it is unnecessary ask far as phasing is concerned, to -introduce any start or rest pulse into the code,`inasmuch as both-the sending and receiving shafts are always in absolute phase relation with each other. Accordingly, such -a system could actually Vbe run on only the intelligence impulses, providing the actuation and vibrating of the printing element on nonfsending of intelligence signals is not a factor.l If this arrangement were not satisfactory, due possibly to the peculiar mechanical construction ofthe printing element to which this might be applied, the start pulse-could be introduced, the polarity of which could be governed in the'same way-that such polarity is now governed in simplex or start-stop systems. In no case, however, would it befnecessary to add the frest pulse, inasmuch asperfect phase and synchronism is always maintained between motors 9 andY 8. It canreadily be seen now, .that if the receiving shaft of said printing element is actuated'in the manner described, vany ungoverned motor indicatedv at 15, [through proper gearing, can be used to operate' the heavier mechanismsY of the printing element,'namely,.printer element, tape feed element, letters and figures shift element, any transfer elements, etc. i

jIt is possible that in starting in the morning or at any other time, motor 8 will not be startedat exactly the same time'as motor 9. .The result rmight be that although the motors 'arej'in perfect'speed synchronism, the phase 'relationship between the armatures of said :motors is not correct;v Irhave therefore'inter- 'i 65 posed betweenshaftsj?l and 5, the planetary 'gin the amount shown.'`

gear unit 6. To those versed in gearing, it is `known that in planetary gearing, one element of the unit may be kept turning while the other element is stationary, without any tendency to jam or load up any-of the gear units. This system can be readily applied to this printer, and considering the knob 14 as a stationary element in this'planetary gearing, it is obviousthat by turning knob 14 a certain amount, we can change the phase relationship between shafts 7 and 5 and thus very readily bring pin barrel 1 into exactly the right phase relationship with the signals supplied from'sending brush 10.

As is known to those versed in the art, the multiplex system now in use in this country maintainssynchronismby the use of a method ,of correcting the position of the receiving distribu'l or brushes from the reversals ofcurrent'on the line. 'That is, the receiving distributor'is run slightly faster than the send ing distributor, and the receiving brushes are one end of a received signal to the other.

These difficulties are overcome by my invention.

A clear and'concise description of the operation of the method generally used for correction in multiplex systems can be had by reference to Patent 1,253,889 issued tofS. W. Rothermel on January 15, 1918. A

It can readily be seen that the use ofV th method therein described will result in a relative shiftof the brush with relation to the signal as shown in Figs. 2 and 3 and a resultant loss in the margin, dependent upon the amount of brush shift for the correction.

In Fig. 2 I have shown the preferred relation between the incoming signals andthe passing of the'brushes over the distributor segments. VvPerfect operation would result in this state at all times. This effect and the resultant full margin will be secured by application of my invention to the sending and receiving distributors. i

Fig shows theresult of brush shifting. The full line represents the incoming wave position relative to the brushes vpassing over the receiving segments before correction, while the dotted line represents the relative positions of wave and brush after correction. It is seen therefore that the shift is effectively the distance between the two wave representations which decreases the range mar- As stated before, my inventionwill overcome this diiiicult'y andhave the added advantage 'of not losing synchroni'sm on line hits or opens.` It is merely necessary to employ synchronous Vmotors driven fromv the same chain power `source,for both the receiving'and transmitting distributors, and to use the same differential geared couplingon the receiving brush shaft to find the correct phase. Y While this changing yrelation between brush travel and signal is a bad factor in terminal operation of multiplex, it is ymuch yworse in rotary repeaters as it is really the factor. which limits the number of rotary repeaters on a line.k y 5 It will readily be seen that in a repeater suchpas isshown in Fig. 4, any surging of the brushes on thesegments yof the distributor will tend to elongate said signal on which the surge occurs, and as a result will necessitate a correction on every repeater thereafter. Application of-my invention to the distributors in use for theserot'ary repeaters eliminates this trouble andpermits any number of rotary repeaters tobe puty on one circuit. As will be seen fromV Fig. 4, both distributor brushesl at the repeater station maybe operated from the same synchronous motor 8 through a double differential gear; Each v differentialy is provided with a phase adjust- :iig knob 14 as described in connection with 1g. 1. n f

This system as above described, has only been shown in application to start-stop and multiplex telegraphy. It is obvious, however, that such a systemcould be very readily used in anycommunication system inwhich synchronous and correct phase operation is a vital factor. This scheme could very readily be used, for example, in telegraph picture transmission or in the so-called ktelevision machines of which there are a number, or in any system where a portion of a receiving mechanism must be maintained in synchronism Ywith the transmitting element. i

While my invention has,V been illustrated as employing a power. net-work,such as the alternating current net-work for supplying a number of Vwidely separated cities or communities with electricilight and power, it will be understood that my invention may be practiced rby employing so-called high or intermediate frequency carrier currents for maintaining the communication system in .-synchronism. This carrier current may be transmitted over a power net-work such asy Vdescribed above, or it may be transmitted' overthe same conductor with the intelligence pendent motors for driving the other movable elements of said-printers.

2.' The method of operating a start-stop y telegraphsystem which consists in maintaining the pin barrels of the printers in synconnected to saidfpower 'systemy for driving the synchronous units of said transmitters andy receivers, and independent motors for driving the remaining movable elements of saidsignal apparatus.

4. The ymethod of operating a communication system wherein the sender and receiver embody motor-actuated line-connected transmitting and reproducing elements respectively that are essentially maintained in synchronous operation, which consists in actuating the motor-driven elements synchronously and maintaining exact phase relationship thereof by connection with a power system, actuating the reproducing elements of the receiver by impulses sent over the line from the transmitting element and independent motors yfor ,driving they remaining movable elements of the receiver.

In testimony whereof I aliix my signature.

ROBERT F. DIRKES.

' signals but independently of them and of the n other driving sources.

.I claimrn y Y n 1. In a start-stop system, the combination 60 transmitting signalsbetween said elements, an alternating current ycircuit separate from f said line, synchronous motors operated from said circuit for driving the pin barrels of ofa transmitter, a receiver, and a line for f '65 said transmitters and receivers, and inde- 

